Chapter 8: Problem 24
Evaluating a Limit In Exercises \(11-42,\) evaluate the limit, using L'Hopital's Rule if necessary. $$ \lim _{x \rightarrow \infty} \frac{5 x+3}{x^{3}-6 x+2} $$
Short Answer
Expert verified
The limit as \(x\) approaches infinity is 0.
Step by step solution
01
Identify the indeterminate form
Here the function approaches \(\frac{\infty}{\infty}\) as \(x\) approaches infinity. This is an indeterminate form and it propmts us to apply L'Hopital's Rule. The limit is therefore: \( \lim_{x \rightarrow \infty} \frac{5 x+3}{x^{3}-6 x+2}= \lim_{x \rightarrow \infty} \frac{\infty}{\infty}\)
02
Apply L'Hopital's Rule
We differentiate the numerator and the denominator separately: \( \frac{d}{dx} (5x + 3) = 5 \) and \( \frac{d}{dx} (x^3 - 6x +2) = 3x^2 - 6 \). By applying the rule, we get \( \lim_{x \rightarrow \infty} \frac{5}{3x^2 - 6}\).
03
Evaluate the Limit
As \( x \) approaches infinity, the term \( 3x^2 - 6 \) also goes to infinity. Therefore, we get an expression of the form \( \frac{a}{\infty} \) (where \(a\) is a finite number). The limit of such an expression is 0.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Indeterminate Forms
In calculus, an indeterminate form happens when you try to evaluate a limit and the result isn't immediately clear. It's like a mathematical puzzle where the usual rules don't directly apply. Indeterminate forms often show up as expressions like \( \frac{0}{0} \) or \( \frac{\infty}{\infty} \). These forms look like they could mean anything, which is why they need special approaches for evaluation.
Think of indeterminate forms as a signal that we need a different tactic to solve a problem.
Think of indeterminate forms as a signal that we need a different tactic to solve a problem.
- Common indeterminate forms are \( 0/0 \), \( \infty/\infty \), \( 0\cdot\infty \), and others like \( \infty - \infty \) and \( 1^\infty \).
- They frequently arise in calculus when analyzing limits, especially those involving complex fractions, exponentials, or logarithms.
- L'Hôpital's Rule is a powerful toolkit for solving indeterminate forms related to limits.
Limits at Infinity
When dealing with limits, "at infinity" refers to analyzing what happens to a function as the variable approaches either very large positive or negative values. Mathematically, it's expressed as \( x \rightarrow \infty \) for positive infinity or \( x \rightarrow -\infty \) for negative infinity. Think of it as examining the behavior of a function on a never-ending path.
Understanding limits at infinity is crucial for:
Understanding limits at infinity is crucial for:
- Determining the end-behavior of polynomials and rational functions.
- Analyzing asymptotic behavior, which is how a function behaves as it approaches a horizontal line or value.
- Applying it to real-world situations, like certain engineering problems or natural phenomena.
Differentiation
Differentiation is a fundamental concept in calculus that involves computing the derivative of a function. A derivative represents the rate of change of a function with respect to a variable. Imagine it as a snapshot of a function's slope at a particular point.
To differentiate effectively, consider:
To differentiate effectively, consider:
- The power rule, useful for polynomials, states: if \( f(x) = x^n \), then \( f'(x) = nx^{n-1} \).
- Applying to individual terms in a polynomial involves breaking down the function into simpler parts.
- Differentiating allows you to simplify complex expressions, especially in finding limits.